hydraulic symbols and their functions pdf Saturday, December 12, 2020 2:44:14 AM

Hydraulic Symbols And Their Functions Pdf

File Name: hydraulic symbols and their functions .zip
Size: 2174Kb
Published: 12.12.2020

Symbols based on ISO and 2. Try our FREE training on virtual test rigs here. Hydraulic symbols provide a clear representation of the function of each hydraulic component. Laying each symbol out on the page in the same sequence the components are used in the circuit allows people to understand the complete function of the hydraulic equipment. It would be nice to think that each type of valve had its own symbol and that all valves can be clearly defined, however, the international standard has been the focus of much discussion for many years and is something of a compromise.

Hydraulic machinery

Hydraulic machines use liquid fluid power to perform work. Heavy construction vehicles are a common example. In this type of machine, hydraulic fluid is pumped to various hydraulic motors and hydraulic cylinders throughout the machine and becomes pressurized according to the resistance present. Hydraulic systems, like pneumatic systems , are based on Pascal's law which states that any pressure applied to a fluid inside a closed system will transmit that pressure equally everywhere and in all directions.

A hydraulic system uses an in-compressible liquid as its fluid, rather than a compressible gas. The popularity of hydraulic machinery is due to the very large amount of power that can be transferred through small tubes and flexible hoses, and the high power density and wide array of actuators that can make use of this power, and the huge multiplication of forces that can be achieved by applying pressures over relatively large areas.

One drawback, compared to machines using gears and shafts, is that any transmission of power results in some losses due to resistance of fluid flow through the piping. Joseph Bramah patented the hydraulic press in To supply large scale power that was impractical for individual steam engines, central station hydraulic systems were developed. Hydraulic power was used to operate cranes and other machinery in British ports and elsewhere in Europe.

The largest hydraulic system was in London. Hydraulic power was used extensively in Bessemer steel production. Hydraulic power was also used for elevators, to operate canal locks and rotating sections of bridges.

In normal cases, hydraulic ratios are combined with a mechanical force or torque ratio for optimum machine designs such as boom movements and trackdrives for an excavator.

Cylinder C1 is one inch in radius, and cylinder C2 is ten inches in radius. The downside to this is that you have to move C1 a hundred inches to move C2 one inch. The most common use for this is the classical hydraulic jack where a pumping cylinder with a small diameter is connected to the lifting cylinder with a large diameter.

This combination is actually the same type of force multiplication as the cylinder example, just that the linear force in this case is a rotary force, defined as torque. Both these examples are usually referred to as a hydraulic transmission or hydrostatic transmission involving a certain hydraulic "gear ratio". A hydraulic circuit is a system comprising an interconnected set of discrete components that transport liquid. The purpose of this system may be to control where fluid flows as in a network of tubes of coolant in a thermodynamic system or to control fluid pressure as in hydraulic amplifiers.

For example, hydraulic machinery uses hydraulic circuits in which hydraulic fluid is pushed, under pressure, through hydraulic pumps , pipes, tubes, hoses, hydraulic motors , hydraulic cylinders , and so on to move heavy loads.

The approach of describing a fluid system in terms of discrete components is inspired by the success of electrical circuit theory. Just as electric circuit theory works when elements are discrete and linear, hydraulic circuit theory works best when the elements passive component such as pipes or transmission lines or active components such as power packs or pumps are discrete and linear.

This usually means that hydraulic circuit analysis works best for long, thin tubes with discrete pumps, as found in chemical process flow systems or microscale devices. The fluid is then filtered and re-pumped. The path taken by hydraulic fluid is called a hydraulic circuit of which there are several types. Open-loop: Pump-inlet and motor-return via the directional valve are connected to the hydraulic tank.

The term loop applies to feedback; the more correct term is open versus closed "circuit". Open center circuits use pumps which supply a continuous flow. The flow is returned to the tank through the control valve's open center; that is, when the control valve is centered, it provides an open return path to the tank and the fluid is not pumped to a high pressure.

Otherwise, if the control valve is actuated it routes fluid to and from an actuator and tank. The fluid's pressure will rise to meet any resistance, since the pump has a constant output.

If the pressure rises too high, fluid returns to the tank through a pressure relief valve. Multiple control valves may be stacked in series. This type of circuit can use inexpensive, constant displacement pumps. Closed-loop: Motor-return is connected directly to the pump-inlet.

To keep up pressure on the low pressure side, the circuits have a charge pump a small gearpump that supplies cooled and filtered oil to the low pressure side. Closed-loop circuits are generally used for hydrostatic transmissions in mobile applications.

Advantages: No directional valve and better response, the circuit can work with higher pressure. The pump swivel angle covers both positive and negative flow direction.

Disadvantages: The pump cannot be utilized for any other hydraulic function in an easy way and cooling can be a problem due to limited exchange of oil flow. High power closed loop systems generally must have a 'flush-valve' assembled in the circuit in order to exchange much more flow than the basic leakage flow from the pump and the motor, for increased cooling and filtering.

The flush valve is normally integrated in the motor housing to get a cooling effect for the oil that is rotating in the motor housing itself. The leakage flow as well as the extra flush flow must be supplied by the charge pump. A large charge pump is thus very important if the transmission is designed for high pressures and high motor speeds. High oil temperature is usually a major problem when using hydrostatic transmissions at high vehicle speeds for longer periods, for instance when transporting the machine from one work place to the other.

High oil temperatures for long periods will drastically reduce the lifetime of the transmission. To keep down the oil temperature, the system pressure during transport must be lowered, meaning that the minimum displacement for the motor must be limited to a reasonable value.

Circuit pressure during transport around bar is recommended. Closed loop systems in mobile equipment are generally used for the transmission as an alternative to mechanical and hydrodynamic converter transmissions. Large wheel loaders for instance and heavy machines are therefore usually equipped with converter transmissions.

Recent technical achievements for the converter transmissions have improved the efficiency and developments in the software have also improved the characteristics, for example selectable gear shifting programs during operation and more gear steps, giving them characteristics close to the hydrostatic transmission. Hydrostatic transmissions for earth moving machines, such as for track loaders, are often equipped with a separate ' inch pedal ' that is used to temporarily increase the diesel engine rpm while reducing the vehicle speed in order to increase the available hydraulic power output for the working hydraulics at low speeds and increase the tractive effort.

The function is similar to stalling a converter gearbox at high engine rpm. The inch function affects the preset characteristics for the 'hydrostatic' gear ratio versus diesel engine rpm. The closed center circuits exist in two basic configurations, normally related to the regulator for the variable pump that supplies the oil:.

Load-sensing systems LS-system generates less power losses as the pump can reduce both flow and pressure to match the load requirements, but requires more tuning than the CP-system with respect to system stability. The LS-system also requires additional logical valves and compensator valves in the directional valves, thus it is technically more complex and more expensive than the CP-system.

If the pump flow is high the extra loss can be considerable. The power loss also increases if the load pressures vary a lot. The cylinder areas, motor displacements and mechanical torque arms must be designed to match load pressure in order to bring down the power losses.

Pump pressure always equals the maximum load pressure when several functions are run simultaneously and the power input to the pump equals the max.

This is a new type of LS-system, not yet fully developed. Technically the down-stream mounted compensator in a valveblock can physically be mounted "up-stream", but work as a down-stream compensator.

System type 3 gives the advantage that activated functions are synchronized independent of pump flow capacity. The flow relation between 2 or more activated functions remains independent of load pressures, even if the pump reaches the maximum swivel angle.

This feature is important for machines that often run with the pump at maximum swivel angle and with several activated functions that must be synchronized in speed, such as with excavators.

With type 4 system, the functions with up-stream compensators have priority. Example: Steering-function for a wheel loader. No official standardized name for this type of system has been established but Flowsharing is a common name for it.

Hydraulic pumps supply fluid to the components in the system. Pressure in the system develops in reaction to the load. Hence, a pump rated for 5, psi is capable of maintaining flow against a load of 5, psi. Pumps have a power density about ten times greater than an electric motor by volume. They are powered by an electric motor or an engine, connected through gears, belts, or a flexible elastomeric coupling to reduce vibration. Piston pumps are more expensive than gear or vane pumps, but provide longer life operating at higher pressure, with difficult fluids and longer continuous duty cycles.

Piston pumps make up one half of a hydrostatic transmission. Directional control valves route the fluid to the desired actuator. They usually consist of a spool inside a cast iron or steel housing. The spool slides to different positions in the housing, and intersecting grooves and channels route the fluid based on the spool's position.

The spool has a central neutral position maintained with springs; in this position the supply fluid is blocked, or returned to tank. Sliding the spool to one side routes the hydraulic fluid to an actuator and provides a return path from the actuator to tank. When the spool is moved to the opposite direction the supply and return paths are switched.

When the spool is allowed to return to neutral center position the actuator fluid paths are blocked, locking it in position. Directional control valves are usually designed to be stackable, with one valve for each hydraulic cylinder, and one fluid input supplying all the valves in the stack.

The valve block will be mounted to the machine's frame with a three point pattern to avoid distorting the valve block and jamming the valve's sensitive components.

The spool position may be actuated by mechanical levers, hydraulic pilot pressure, or solenoids which push the spool left or right. A seal allows part of the spool to protrude outside the housing, where it is accessible to the actuator. The main valve block is usually a stack of off the shelf directional control valves chosen by flow capacity and performance. Some valves are designed to be proportional flow rate proportional to valve position , while others may be simply on-off.

The control valve is one of the most expensive and sensitive parts of a hydraulic circuit. The hydraulic fluid reservoir holds excess hydraulic fluid to accommodate volume changes from: cylinder extension and contraction, temperature driven expansion and contraction, and leaks.

The reservoir is also designed to aid in separation of air from the fluid and also work as a heat accumulator to cover losses in the system when peak power is used. Design engineers are always pressured to reduce the size of hydraulic reservoirs, while equipment operators always appreciate larger reservoirs. Reservoirs can also help separate dirt and other particulate from the oil, as the particulate will generally settle to the bottom of the tank.

Some designs include dynamic flow channels on the fluid's return path that allow for a smaller reservoir. Accumulators are a common part of hydraulic machinery. Their function is to store energy by using pressurized gas.


If you wish to contribute or participate in the discussions about articles you are invited to join SKYbrary as a registered user. Virtually all aircraft make use of some hydraulically powered components. In light, general aviation aircraft, this use might be limited to providing pressure to activate the wheel brakes. In larger and more complex aeroplanes, the use of hydraulically powered components is much more common. Depending upon the aircraft concerned, a single hydraulic system, or two or more hydraulic systems working together, might be used to power any or all of the following components:.

Hydraulic Schematic Symbols.pdf

Hydraulic machines use liquid fluid power to perform work. Heavy construction vehicles are a common example. In this type of machine, hydraulic fluid is pumped to various hydraulic motors and hydraulic cylinders throughout the machine and becomes pressurized according to the resistance present. Hydraulic systems, like pneumatic systems , are based on Pascal's law which states that any pressure applied to a fluid inside a closed system will transmit that pressure equally everywhere and in all directions.

Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. If you continue browsing the site, you agree to the use of cookies on this website. See our User Agreement and Privacy Policy.

Bs symbols pdf. The graphic symbols used for electrical components in circuit diagrams are covered by national and international standards, in particular: IEC also known as British Standard BS In electronic circuits, there are many electronic symbols that are used to represent or identify a basic electronic or electrical device. For examination from O-ring inside diameter; d.

Hydraulic Schematic Symbols.pdf

Below are some common illustrations of equipment located on fluids circuit diagrams, followed by descriptions of the most common elements. Later in this article series we will describe some simple hydraulic and pneumatic circuits composed of these circuit elements. Needle valves are used to throttle or shut-off flow of fluids. They usually will vary flow with pressure or viscosity change. Gauges are used to measure the oil pressure at a given point in the system. This is usually measured in PSI or bars.

Out of any topic under the patio-sized umbrella of fluid power, hydraulic symbology garners the most requests from those wishing to learn more about fluid power. Reading any schematic with more than three symbols can be daunting if your experience is limited. This month, I will give you the basics so you know how the standardized lines and shapes are drawn and structured to be universally interpreted.

Airline Hydraulic's Main Page. Basic Symbols. Lines pressure control function. -two or three adjacent squares - directional control. Diamond.

Hydraproducts Blog

Hydraulics symbols are an essential component of hydraulic circuit diagrams. Knowing some of the basic principles will help understand a wider range of symbols. Explaining the common ISO symbols enables a complete hydraulic system to be followed:. Hydraulic pump produces flow. Oil is pumped from the hydraulic reservoir into the system.

Hydraulic symbology 101: Understanding basic fluid power schematics

 Сэр? - Беккер легонько потормошил спящего.  - Простите, сэр… Человек не шевельнулся. Беккер предпринял очередную попытку: - Сэр.

Беккер усмехнулся: - Давненько не летал. Со вчерашнего дня. ГЛАВА 128 Когда Сьюзан проснулась, солнце уже светило вовсю. Его нежные лучи проникали сквозь занавеску и падали на пуховую перину. Она потянулась к Дэвиду.

Когда он был уже почти рядом, Сьюзан поняла, что должна действовать. Хейл находился всего в метре от нее, когда она встала и преградила ему дорогу. Его массивная фигура буквально нависла над ней, запах одеколона ударил в ноздри.